[HN Gopher] A study reveals that deciduous trees' roots remain a...
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A study reveals that deciduous trees' roots remain active in winter
Author : bryanrasmussen
Score : 64 points
Date : 2025-03-22 19:33 UTC (3 days ago)
(HTM) web link (www.creaf.cat)
(TXT) w3m dump (www.creaf.cat)
| londons_explore wrote:
| This seems like the logical result... Underground where
| temperatures are less extreme, there is no good reason to reduce
| growth.
| mapt wrote:
| > "Our results demonstrate that the above-ground and below-ground
| parts of a tree follow separate calendars, allowing for
| underground growth to be prioritized in winter and aerial growth
| at the beginning of spring," says CREAF researcher Paolo
| Zuccarini, a co-author of the study. This divergence could offer
| a strategic advantage: in winter, while the rest of the tree is
| dormant, its roots store reserves of carbohydrates and nitrogen-
| rich substances, such as proteins and amino acids. Thus, when the
| tree 'reawakens', it will have enough nourishment for leaves to
| bud and photosynthesis to resume, which is essential for trunk
| and branch growth. "It's kind of like having building blocks
| ready to use in the spring, when the priority is to produce
| leaves so that photosynthesis can start again," explains
| Zuccarini.
|
| Okay this part makes sense.
|
| > Its findings suggest that forest soils have a greater carbon
| sink capacity than was previously believed, as they accumulate
| carbon all year long rather than only when trees are more active
| and their leaves are photosynthesizing.
|
| This does not. They're not accumulating carbon in winter because
| they're not photosynthesizing carbon dioxide into glucose in
| winter. They're using stored carbon to continue cell division
| (not to mention bribing bacteria & fungi to build a rhizosphere
| with which to harvest nutrients).
| darkerside wrote:
| Probably misinterpretation. They don't accumulate carbon, but
| this activity depletes carbon reserves, increasing capacity to
| accumulate carbon in the summer months.
| zdragnar wrote:
| Sadly, roots respire- meaning that depletion of the carbon
| reserves happens by releasing CO2 (in addition to building
| lignin). It's only when they photosynthesize that plants
| produce more O2 and absorb more CO2 than they release.
| mncharity wrote:
| > It's only when they photosynthesize that plants produce
| more O2 and absorb more CO2 than they release.
|
| And even narrower than that. I fuzzily recall seeing
| rainforest curves, where only for some hours around noon
| were trees net producers. Hmm... though perhaps that was
| for forest-not-just-tree?
| damnitbuilds wrote:
| This seems like something that they could have and should have
| found out hundreds of years ago?
| squircle wrote:
| Not until its published? Have not read the article but I
| thought this was common knowledge.
| Maciek416 wrote:
| Winter root growth is widely-observed amongst people who work
| with tree roots annually (bonsai hobbyists and professionals,
| commercial ornamental tree growers, especially propagation-
| adjacent roles) in milder temperate climates (eg: Pacific
| Northwest).
|
| In my time studying bonsai (past 7-10y) in every winter (Jan-
| Mar) I've repotted (anywhere from partial to full bare
| rooting, partial to full root structure editing) many PNW-
| native deciduous trees (alders, bigleaf + vine maples,
| cottonwoods, etc) as well as non-PNW-native deciduous
| (birches, beeches, elms, maples, hazels, hornbeams,
| stewartia, bald cypress, cherries/plums, quinces, snowbells,
| etc). In somewhat-mild-and-milder climates there is _always_
| some root growth going on. Such winter root growth is much
| more aggressive in conifers, particularly pines, but also in
| spruces, cypress-family species (junipers).
|
| Here's a diagram from a paper showing scots pine and
| rowan/ash adding either root or vegitative growth in various
| parts of the year:
|
| https://imgur.com/a/qF4oQ8a
|
| Temperate trees collect or spend carbon in the warm parts of
| the year, i.e. between bud-break and mid-summer. In cooler
| parts of the year, they do various things: store it in the
| wood, move it around (redistribution + retranslocation),
| spend it (future-season buds + cambium + root expansion) or
| carefully avoid spending it (dormancy).
|
| Even in these periods they're still collecting sunlight if
| they can, quite a few deciduous species can photosynthesize
| at least a little bit directly through their bark -- young
| twigs have much thinner bark even in trees that get very
| rough bark (eg: black cottonwood). And evergreens are
| collecting sunlight any time mild-or-warmer conditions are in
| play.
|
| Trees are active in some shape or form any time they are able
| to be. If you live in USDA hardiness zone 7 or warmer and
| have trees/shrubs outside you can notice this more easily
| than in colder climates (where the grow/no-grow seasons are
| more sharply bounded). Roots are not the only thing expanding
| in winter. Take a picture every day of a branch on a
| deciduous or evergreen tree and you'll see bud expansion.
| destitude wrote:
| Yeah but they aren't making this clear and see people
| misinterpreting this not realizing that it is in temperate
| forests only. I don't see how any tree roots can be formed
| when frost line is feet below the surface.
| ledauphin wrote:
| i'd read several state Ag agencies that have known this. It's
| why you keep watering newly planted trees even after their
| leaves fall, until the ground freezes. The roots will keep
| growing.
| hoeoek wrote:
| Cool! As a forester, this is interesting to see being researched.
| Many models in our field link biomass growth strictly to seasonal
| temperature thresholds, often considering trees to be 'growing'
| only when mean daily temperatures exceed 5 or 10 degrees Celsius
| for a consecutive week in spring, and 'idle' otherwise. So
| basically not accounting for this new "off-season growth", older
| research are overlooking a bunch of details and insights into
| growth dynamics. Using coniferous/decidious species as random
| effects in models has shown to have an effect - this might be
| why.
| abakker wrote:
| Its interesting because last year I did an experiment where I
| put ~6" of wood chip mulch and slow release fertilizer over the
| root zones of several trees (climate 6a), and now that its
| spring, every tree that got the thick coat of mulch has leafed
| out or budded significantly more than those that just got
| fertilizer. (sample size of around 10 trees in bad dirt in
| boulder. YMMV)
| 0xbadcafebee wrote:
| I mean, could have been the fertilizer, or could have just
| been an insulating layer?
| zdragnar wrote:
| Since OP mentioned both with and without the mulch got
| fertilizer, it's definitely insulation.
|
| They also mentioned "bad dirt" as well, so there's a very
| good chance the mulch also helped with moisture retention.
| abakker wrote:
| yeah, we have alkaline expansive clay, so moisture
| retention was an objective. I added the nitrogen to
| offset the fact that fresh wood chips tend to be a
| nitrogen sink rather than a source.
|
| I theorize that thermal protection and moisture retention
| together have kept those plants happier.
| taeric wrote:
| My mental model for deciduous trees was that they drop their
| leaves as a form of biological warfare against the shrubs below.
| I'm also growing to the idea that it is a way to lower their
| footprint against winds in the winter.
|
| Would be neat to see more studies like this that look at the way
| they grow. Reminds me of the fun video that talks about where
| they get their mass. Related heavily to how and where people lose
| weight.
| moate wrote:
| In your mind, how does dropping leaves harm the shrubs?
| Wouldn't it allow for more light to pass down to the forest
| floor? It feels like the tree's response to shrubs was "grow
| taller to maximize sun exposure"
|
| I feel like the conventional wisdom that this is a response to
| environment(conserve energy/lower wind resistance) make more
| sense than "offensive deterrent for competing plants" even more
| so when you consider that every leaf dropped is biomass that
| the tree had already taken in and utilized, but now it's giving
| it up. Maybe a pro-symbiotic move whereby dropping the leaves
| provides shelter/biomass for beneficial insects that could
| provide root aeration or soil enrichment would be another
| reason?
| taeric wrote:
| I'm largely going by what I see in my yard. If I want any of
| the ground shrubs to not die every year, I have to make sure
| they are not drowned in leaves.
|
| Note that I'm not claiming the leaves are necessarily bad.
| They make pretty good mulch and such. But, without tending to
| uncover the smaller plants, they do a pretty good job of
| killing the things below the tree.
| Maciek416 wrote:
| It affects seedling recruitment for sure. Some species love
| to start beneath leaf mulch and there is probably something
| out there that would colonize your leaf field hard and fast
| if it were given the chance. I collect red alder seedlings
| in timber clearcutting areas, and often find that they've
| had to twist/push their way through 6-12" of slash
| (clearcutting debris) to reach light and finally grow
| upwards. Quite a few conifers can push upward through many
| inches of needle duff as well.
| Maciek416 wrote:
| I think conserving energy in cold months is close to the
| biggest factor.
|
| Regarding the dropping of biomass, in both deciduous and
| evergreen species, some of the substances from the retiring
| leaves/needles are reclaimed by trees ("retranslocation") and
| pulled out of the leaf before letting go of the leaf. In
| species like pines it'll be the second or third (or older,
| sometimes much older) retiring needles and in species like
| maple or beech it'll the be the entire foliage. Mass useful
| to soil ecosystems still falls but the tree grabs what it can
| in the late months of the year, hence the color change.
|
| One thing the grandparent comment doesn't talk about much is
| the cost (in sugar) of both building and thereafter
| maintaining leaves and the related tradeoffs. Building a
| fully winter-tolerant broadleaf is more expensive sugar-wise
| than building a winter-interolerant leaf. A sugar maple in
| Quebec, where the season is shorter than (say) Oregon is
| going to compete in its niche better if it can attain surface
| area quickly at the start of the growing season, and that is
| better done with a winter-intolerant, more relatively
| delicate leaf. An evergreen leaf takes more time and mass to
| build and has to have more limited surface area or armor
| (cuticle) to tolerate such winters.
| AngryData wrote:
| Decaying leaves do change the ph of the soil and can leave a
| wet heavy mass that new sprouts have trouble sprouting
| through and seeds have trouble getting through to the soil.
|
| There is no reason shedding leaves has to only be for one
| single purpose like weather protection, saving energy, or
| trying to prevent competition, it can be all at once.
| jnellis wrote:
| The bulk of roto-rooter calls to clear home sewer lines of tree
| roots happens during winter.
| naikrovek wrote:
| I feel like I already knew this somehow. I'm sure I wanted to
| discover this as a child and cut a root during winter so that I
| could see if it healed. more likely I probably put the end of a
| root into some water with food coloring in it and came back later
| to see that food coloring had moved up the root.
| y-c-o-m-b wrote:
| I always assumed the roots kept growing, so I didn't know that
| wasn't already an established idea. That kind of strikes me as
| strange and interesting. I figured it was common sense?
|
| This was extremely evident by the red maple on our curb
| destroying the sidewalk even through the winter months. Even my
| dwarf magnolia tree has a notable increase in its trunk size in
| its dormant phase.
| destitude wrote:
| This is still in temperate forests. It still isn't clear to me
| if this is true where frost lines are feet below the surface.
| How can the roots grow in frozen soil?
| cwmoore wrote:
| I can imagine root tips advance by thermally or chemically
| melting ice or frozen soil.
| mvdtnz wrote:
| This is common knowledge. What a waste of time and effort.
| volleygman180 wrote:
| When controlling invasive plants like honeysuckle using
| glyphosate, one of the more responsible approaches is to wait
| until all of the trees have lost their leaves in the fall and
| entered dormancy. The idea being that because the honeysuckle
| still has its leaves, you can safely use glyphosate on it with
| minimal to no impact on the rest of the ecosystem. I've always
| had my doubts (particularly due to studies on mycelium being
| exposed to glyphosate), but this is one of best practices that
| conservation departments recommend.
|
| With this new study, it opens the possibility that trees may
| still have root absorption during the winter season. I feel like
| it is further evidence of how glyphosate likely always impacts
| the ecosystem and has no truly safe usage
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